For transferring a yarn in a surface drive, turret type automatic winder that has been heretofore proposed, bobbins are driven by means of an independent electric motor while a traverse speed is lowered to a speed that is most suitable for forming a transfer tail. A traverse cam roll is shifted by a pneumatic cylinder or other known means so as to bring a yarn in contact with a yarn gripping device provided at an end of an empty bobbin or on an empty bobbin holder and to make the yarn gripping device grip the yarn. A yarn portion between the yarn gripping device and a fully wound bobbin is cut by means of a cutter associated with the yarn gripping device to wind the yarn on the empty bobbin. As soon as a transfer tail is formed, the traverse cam roll is restored to its normal position and simultaneously the traverse speed is accelerated to the speed upon normal winding, and an electric power source for said bobbin driving motor is switched off while urging the empty bobbin to a drive roll, whereby the winding is achieved according to a surface drive system.
According to this prior art method, by employing a reliable and rigid yarn gripping device manufactured carefully, the rate of success in an automatic yarn transfer could be made 100%. However, in the case of a bobbin holder rotating at a high speed exceeding 10,000 rpm or a yarn gripping device associated with such a bobbin, it has been difficult to reliably and rigidly grip a yarn against a large centrifugal force and a large wind pressure. In practice, sometimes it occurred that winding on an empty bobbin after a yarn transfer was acheived by making use of a yarn only momentarily captured by the yarn gripping device or a partly gripped yarn, and in some rare cases there occurred a failure. More particularly, sometimes it occurred that a yarn once captured by the yarn gripping device was made to float up by a centrifugal force or a wind pressure. Tension of the yarn extending from the transfer tail portion to the start winding portion of the bobbin was slackened which caused the yarn to float up and to wind itself around the drive roll, resulting in failure of the transfer. In addition, there was a disadvantage that the transfer tail was loosened as it was pulled by the yarn gripping device when the fully wound bobbin was removed from the winder in the case of an automatic winder having a yarn gripping device provided on a bobbin holder, or when the yarn gripping device was removed from the fully wound bobbin in the case of an automatic winder having a yarn gripping device provided at an end of a bobbin, and thereby great inconvenience was encountered in handling the yarn in subsequent processes. In other words, there was a disadvantage that the transfer tail was not as good a transfer tail as is required in the subsequent processes.
In addition, it has been found that the abovedescribed prior art method for transferring a yarn proposed in the prior art is disadvantageous in view of the problem of yarn quality with respect to critical and delicate yarns such as the partially orientated yarns (POY) which have been developed recently. According to the above-described method, just before and after the transfer operation the yarn is wound in the outermost layer on the fully wound bobbin and in the innermost layer on the empty bobbin, and a trash yarn or a waste yarn is not produced. However, in practice, a partially orientated yarn, which is a delicate yarn, has its physical properties changed by a variable tension that is inevitably generated upon transfer of the yarn. This yarn having changed properties is the yarn portion that has been wound by the winder just before and after the transfer of the yarn. The yarn having changed properties just before the transfer could be removed, if necessary, by paying out the outermost layer of the fully wound bobbin and throwing it away, because it was wound in the outermost layer of the fully wound bobbin. On the other hand, the yarn having changed properties just after the transfer could not be removed, because it was wound just on the empty bobbin as a transfer tail and the innermost layer and a normal yarn is wound thereon. Although it was possible to cut away the transfer tail because it was exposed externally, cutting away the once-formed transfer tail was meaningless, and also the problem of mixing of a changed yarn was not resolved.